Pro: + good drumkits included + easier handling than LM-4
Con: - overpriced compared to competitors - just basic sample treatment - old LM-4 .fxb/fxp can't be loaded - expensive upgrade for LM-4 users
After the predecessor LM-4 missed the connection to current leading drum VSTi (complicated kit creation etc), Steinberg has improved some things with this new product. Now you can assign samples to each pad more easily with drag&drop or file dialog (no longer text file torments), edit your velocity layers with your mouse ("only" up to 20 layers for each pad - the old LM-4 allowed 128, but was it really needed?) and treat the samples with a volume envelope, reverse playback or lofi bitcrusher. You can miss filters, pitch envelopes or waveform display.
If you don't consider the price it's a solid usable drum sample player with superb drumkits included covering nearly all needs (XXL version).
But compared to DR-008, RM-III, Battery or Attack, which cost around the same, LM-4 MkII has lost in the categories features and usability. Other drum VSTi with comparable capabilities are much cheaper (i.e. CM SR-202: less outputs+groups, no velolayer but filters+pitchEG for 5UKP).
For an old LM-4 user the upgrade is maybe a bit expensive ($50/$100-XXL) - it should have been free since LM-4 was nearly unusable. But the XXL kits are worth it, sold seperately as the 3CD "Kit Connection" for $150 I wanted to buy them anyway. By the way, they're in the old LM-4 format and so can be imported into DR-008 or RM-2/III :-) If you already have songs with the old LM-4 and don't want to spend time again adjusting pad settings, you should keep it installed since MarkII can't load old banks/instruments, only import .txt scripts.
To sum it up: If you're looking for a good collection of drumkits or don't already have a good drum sample player, you may take a look at LM-4 MarkII if you aren't short of money. If you're already happy with your drum VSTi and your kits you don't need this.